Just hours after reaching a late Monday agreement on the richest contract for a defensive player in NFL history, J.J. Watt was back at NRG Stadium.

He could not sleep. He was restless. He wanted to work out. But the facility doors were locked. He thought the team was playing a joke on him, changing the entry codes. A janitorial person finally let him in — at 3 a.m. Tuesday.

Ladies and gentlemen, Mr. Justin James Watt.

“I have been in the building since 3:30 this morning,” Watt said Tuesday, during a press conference announcing his six-year, $100 million deal. “So I’m going to get some sleep tonight. I need it.”

Watt signed his record contract on Tuesday. He reached an agreement late Monday for a six-year deal that includes $51.876 million guaranteed, the most ever to a defensive player.

“Money doesn’t motivate me, greatness does,” Watt said. “I’m so fortunate I don’t have to worry about the money, so I can focus on the greatness.”

Said Texans owner Bob McNair, to close the press conference, “That’s why he got the contract.”

The press conference begin with this declaration from Texans general manager Rick Smith: “We’ve just signed J.J. to a six-year contract that ensures he will be wreaking havoc on QBs in a Texans uniform for a long time.”

Watt got a little emotional early during his press conference, crying as he recounted his youth in Wisconsin with his close-knit family.

“I’m just a kid from Pewaukee, Wisconsin … who had big dreams who worked hard and who had a great support system around him.”

And Watt said he will return the love to his parents.

“They’ll be all right,” he said. “I can’t tell you what, but they’ll be all right.”

McNair showed a sense of humor at the start of the press conference.

“I was a few minutes late because I had to go down to the pawn shop and pawn my wife’s jewels to take care of (Watt),” he joked.

Then, more seriously, McNair gave Watt a Hall of Fame nod, putting him in the conversation with Texans receiver Andre Johnson.

“We look forward to him being the second person that goes in the Hall of Fame,” said McNair, referring to Johnson likely becoming the first. “Now he’s the best and he’s going to do nothing but get better.”

Watt, the 11th overall pick in the 2011 draft, had two years left on his contract, including a base salary of $1.9 million this year and a $6.9 option year in 2015.

Under the terms of his extension, Watt’s base salaries this year and in 2015 will be $907,385 and $9.969 million. When he signs, he gets $10 million.

Watt’s new deal begins in 2016 and extends through the 2021.

“I hope the people of Houston don’t mind me sticking around for a little while longer because I like it here very much,” Watt said. “I promise to do everything in my power to prove that I can earn this and to be the best player I can be.

“I want to go out there and try to (pretend) like I’m underpaid. I’m gonna work my butt off.”